The Onigiri (Omusubi) FAQ

22 Aug 2008 by maki

I have written quite exhaustively about onigiri, or rice balls, here on Just Bento as well as on Just Hungry. Many people have asked similar questions about onigiri, which seem to just be gaining and gaining in popularity these days. So I’ve assembled a list of Onigiri FAQs (Frequently Asked Questions). I’ll update this list when I see (or remember) other questions periodically.

Basics and culture

What is an onigiri? An onigiri is a savory (salty) compressed ball of rice. It often has a filling or a coating of something savory, but there are also onigiri made of pre-flavored/mixed rice, as well as plain rice onigiri simply made with salt.

How do you pronounce it? o-NI-gi-ri (short 0 at the top, not oh or ooh)

How is it written in Japanese? most often おにぎり (all in hiragana); very occasionally お握り

My Japanese friend/my Japanese grandmother/my Hawaiian uncle calls it something else… Onigiri are also often called omusubi （おむすび）. Some more obscure regional names include nigirimama and oninko. You can also drop the honorifico and call it musubi, nigiri, or nigirimeshi (which literally means “hand-pressed rice”. What you call it just depends on where you grew up! In Hawaii, a rice ball is called a musubi mostly. There was a big wave of emigration from Japan to Hawaii in the late 19th century, mainly from the western/southern parts of the country, which probably accounts for the use of musubi.

Why do anime and manga characters love onigiri so much? Onigiri is Japanese comfort food, because Japanese people love rice. Rice is the main staple of Japanese cuisine. (In the movie Kamome Diner (kamome shokudo), discussed at length here, onigiri are called “Japanese soul food”, and I think that is very true.)

Does an onigiri have to be a triangle? No it doesn’t - it can be round, or cylinder shaped, or anything else. There are a few purists who insist that onigiri must be triangular, but I’m not one of them. See Onigiri on parade.

Where can I get onigiri in Japan? Just about every supermarket and convenience store sells them, not to mention train station kiosks, vending machines and more. They are as common as pre-made sandwiches are in the West. (Actually you can get pre-made sandwiches as easily too in Japan.)

Are onigiri just for bentos? In Japan, onigiri is a basic convenience food. People carry them on hikes, car trips, have them for breakfast, as late night snacks…etc.

Are onigiri a Japanese invention? They probably are, because of the nature of Japanese style rice (slightly sticky). This type of rice, also called uruchimai, came into wide use around the 11th or 12th centuries, and onigiri may have come into existence then. In China you have steamed glutinous rice wrapped in leaves, but that’s a bit different from onigiri. (see okowa onigiri made from sticky rice)

Is Spam Musubi Japanese? Spam musubi is a product of Hawai; it was probably created by immigrants of Japanese descent. Spam was virtually unknown until fairly recently in much of mainland Japan. (Spam is fairly popular in Okinawa, which was occupied until the 1970s by the United States and still has a U.S. military base. It’s also very popular in South Korea. Both regions, as far as I can find out, got their Spam habit from Americans.) Personally, I just can’t make myself like Spam in any form, so you won’t see any spam musubi recipes on this site - sorry! There are plenty of spam musubi recipes online however - see this one on Lunch In A Box, or this step by step on Cooking Cute.

Nutrition

How many calories are in an onigiri? It depends on how big it is or how much rice is used to make it. A typical onigiri has about 1/2 cup of rice, so it’s around 100 calories plus whatever is used for the filling.

Does an onigiri have to be made with white rice? You can also make it with brown rice, as long as it’s medium-grain Japonica rice or short-grain glutionous rice. See Looking at rice.

Are onigiri diet food? Well, that depends on how big they are! Many people find onigiri more filling than sandwiches, but that’s a subjective thing of course.

Do I have to use Japanese rice? What about jasmine rice (or other types of rice)? An onigiri has to stay in a ball shape, so the rice has to be glutinous enough that the grains stick together. That means that long grain rice types like jasmine and basmati are not, I repeat not, suited to onigiri. (I feel very strongly about this.) Sure, mushy, overcooked rice will glue together if you mash it hard enough, but it will not taste nice at all. The most suitable types of rice for onigiri are medium grain or short grain. See Looking at rice for different types of rice. If you can’t get Japanese type rice (or ‘sushi’ rice) easily where you live, Italian rices used for risotto can be substituted.

Does an onigiri have to have a filling? No it doesn’t! The most basic type of onigiri is a shio musubi (塩むすび）, a plain rice onigiri with salt on the outside. This is the kind of onigiri that was carried around in feudal times by samurai and foot soldiers on the warpath. It’s a great way to enjoy simple, well cooked good rice.

What are traditional onigiri fillings? A list and photos of the most common traditional fillings are on the Onigiri on Parade page. The top three traditional fillings are: umeboshi (pickled plums), shake (salted salmon - how to make your own from fresh salmon) and okaka (katsuobushi or bonito flakes flavored with soy sauce).

Non-traditional fillings? Anything you can imagine! Some suggestions that readers have made in the past include: chopped up olives, anchovies, pickles, a small meatball, cooked chicken, sausage meat, chopped up Spam, corned beef… as long as it’s not too wet, compact and a bit salty, anything can be a good onigiri filling.

Help! My onigiri fall apart! This could either be due to using the wrong kind of rice (long grain rice, jasmine rice, basmati rice, etc. are not sticky enough to make a rice ball with), improper cooking of rice (it should not be too dry/hard OR too sticky/gluey) or using a filling that’s so oily or watery that the oil/water seeps out into the rice, making it fall apart.

Do onigiri have to be wrapped in nori seaweed? No they don’t, though a wrapping does help to keep the rice together. Again see Onigiri on parade. If you want to go wrapping-less but your onigiri falls apart before you can eat it, try transporting them wrapped in plastic wrap. You can even buy special cute onigiri wrapping film!

I hate nori…alternative wrappers? A popular wrapper is salted fresh shiso leaves. (I must confess that when I was a kid, I hated nori! But now as an adult I love it, so it is quite possibly an acquired taste.) Other wrappers include tororo kombu (a thin, salty form of kombu seaweed) and usuyaki tamago (thin omelettes).

Onigiri safety and transport

Can I freeze onigiri, and if so how? Yes onigiri can be frozen very successfully. Just wrap them individually in plastic wrap (cling film), and then in a freezer box or bag to protect it from freezer burn. You can defrost the onigiri in the refrigerator gradually, at room temperature, or zap it in the microwave. See Keeping onigiri fresh and more Don’t keep frozen onigiri in the freezer for too long, or they will eventually get freezer burn.

How do I prevent onigiri from getting dried out? Keep them well covered/wrapped up.

How long do onigiri last in the refrigerator? How do you keep them safe to eat? This mainly depends on the filling as well as how much salt you use on the surface when you make the onigiri. If you use tuna with mayonnaise or any filling with mayonnaise in it, do not keep more than a day to be safe. If you use traditional fillings, especially umeboshi (pickled salty plums) they will last a lot longer, but no more than a couple of days. Umeboshi has natural antibacterial qualities, so is the ideal filling for onigiri that have to be held for some time - say, made the evening before to be eating or lunch on the road the next day.

In any case, you should make onigiri with adequate salt on the outside, completely cooked fillings (never ever use raw/uncured fish or rare meat) and always use freshly cooked (ideal) or defrosted/reheated rice. If the weather is very warm and humid and you have used spoilable fillings such as tuna/mayo, consider packing your onigiri with an icepack (see Summer Bento Safety).

You shouldn’t eat onigiri that has been around outside of proper refrigeration for more than a day. Anecdotally, I have eaten onigiri that was a day old (made the morning before and eaten for breakfast) that had been in packed in a paper back and thrown on the back seat of a car, not in a cooler, and survived without any problems (it was in the fall, not midsummer), but you shouldn’t do this regularly! The fillings used that time were umeboshi and salty salmon, for what it’s worth - no tuna-mayo or crab salad or other highly perishable filling.

(I’ve seen a note on this ehow.com page that blithely states that “you can store onigiri refrigerated for up to a week”. No you can not! Please, use common sense and be safe not sorry. )

Other questions

Can I use sweet fillings for onigiri? Fundamentally you can use anything you like - it’s your food! However, in Japan if you make a ball of rice (which is often sweetened itself, and pounded partly or fully to a sticky paste or dough) and filled with something sweet it becomes confectionery or wagashi. Some wagashi that take the rice-with-sweet-filling form include daifuku, mochi of various kinds, yatsuhashi and so on. The wagashi that’s closest to the idea of a sweet onigiri is probably ohagi or botamochi, glutinous rice “onigiri” of sorts which are filled, covered or both with sweet bean paste, kinako (toasted soy bean powder), sesame seeds and so on. So, to Japanese sensibilities an onigiri is something savory, not sweet.

What’s the difference between sushi and onigiri? Again it’s a matter of how things are normally categorized in Japanese cooking, but generally speaking anything made with vinegar flavored rice, or sushi rice (sushi meshi or shari) iis sushi. So you could make an onigiri-shaped item with shari, and call it an onigiri, but if a Japanese person ate it s/he would probably think it’s sushi in an onigiri shape. Nigiri-zushi, the best known sushi shape with a little ball of rice topped with fish or something else, is sushi that has been shaped with the hands (nigiru) - the same word that forms part of the word onigiri.

Onigiri in the movies - two Japanese movies that feature onigiri prominently (Supermarket Woman and Kamome Diner). By the way, in Kamome Diner there is a scene where the owner of the Kamome Diner (a small Japanese cafe-restaurant she opens in Helsinki of all places) and her new friends are testing out alternative fillings for onigiri that they think may be more to the taste of Finnish people. They test things like crayfish, reindeer meat, pickled herring, and so on. But ultimately they come to the conclusion that the best fillings are the classics, the Big Three traditional fillings mentioned above: umeboshi, shake and okaka. I have to say I tend to agree with this (though I might add grilled tarako to the list too)!

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Recently, I made onigiri with pickles for filling, and they were very tasty. However, I was wondering about using meat for fillings. For example, tonight I am making some awesome chicken curry, and thought that it might make a nice onigiri filler with the leftovers. My question is, how careful do I have to be when using cooked meat (especially chicken) as a filler for onigiri, when I might be carrying it outside of a fridge for a few hours before I eat it. It seems to me that onigiri stay quite cool for a while by themselves, but I'm just a little paranoid anytime I use chicken for anything. I'll probably go buy an ice pack or something for now to keep them near, but I wonder if I need to be careful or not, as it seems like there are a couple "chicken fillers" on the list of recommended fillings anyways.

I prepared my first bento this morning (YAY!)... I used a triangle onigiri mold to fix the hot sushi rice yesterday evening, immediately wrapped it in krewrap and stored it in the freezer overnight. I took it out this morning, put a small amount of oil in the pan, and placed the frozen onigiri on a medium-high setting. The problem was that after turning the onigiri two times, the rice began to fall apart, and the inside was still frozen. SO I took it out, brushed with soy sauce and a LITTLE rice vinegar, and put it back in the pot. It began to get the brown color on the sides, but the rice began to fall apart more and stick to the pan, so I just took it out and packed it. The center still seemed a little cold and slightly frozen. I plan to microwave it at lunch time... :-/

Is there anything I am doing wrong here, or is the rice naturally supposed to break apart a little? Please advise. ANY response is necessary.

It's my intention to grill my onigiri for lunch boxes until I can work up the nerve to do other things.

You should defrost the onigiri, wrapped in plastic wrap so it doesn't lose moisture (which will cause the rice to fall apart) and reheat it all the way through before attempting to cook it in the frying pan. That should work.

I had similar problems when grilling onigiri. One friend told me it was because I was using a mold and not my hands, which I didn't agree with (the rice falls apart more when I try to use my hands). I began practicing more and more with freshly made onigiri until I got it down. You may need to just practice a lot during a time when it doesn't really matter what the rice looks like (like before a dinner when you can just toss the broken onigiri in a bowl and eat it with a fork LOL!).

Basically, make sure that when you're going to grill/fry the onigiri that you pack it pretty tightly, it's easy to not get enough rice in the mold. Also, you have to be really gentle when you're flipping them around. Sometimes (when I'm feeling brave/it's not too hot) I'll just use my fingers to flip them. Make sure you haven't over-oiled the pan, or it'll just be soggy (I usually put a tiny bit of oil in the pan and then wipe it around with a napkin). Also, you may want to refridgerate the onigiri if you're just going to use it the next morning/afternoon, that way you don't need to "over-cook" it in order to thaw. OH! And another thing, I see some people cooking the edges of the onigiri as well, I don't do that, I just fry the two flat sides and call it done. If you're trying to get the edges too, it could see that leading to crumbling.

I'd say that you should just practice to get the exact technique down. I'm pretty good at frying onigiri now, but I can't tell you EXACTLY how to do it, I think it's just practice.

So I made these for a potluck and there's a few things I learned. 1) That is is SOOOOO important to let the rice cool! Like holy crap that was hot! 2) It doesn't take a whole lot to get good at it. I made maybe three or so before they started getting pretty uniform. 3) Tin foil CAN work just as well as cling wrap, maybe better depending on how you use it. 4) (Well, I already knew this, but still...) Tuna and mayo actually won't spoil that quick. I made my onigiri the day before, put them in the fridge, and then carried them with me for a few hours before it was finally lunch time. They were perfectly fine. 5) The nori gets really moist after about five minutes... and 6) I like smaller ones better.

I (accidentally) found that if regular rice is left to cook just a little longer, it will stick together. I don't know if this will work with anyone else, but it has worked well for me. Just let you know. :)

It's not in the least bit traditional Japanese, but one filling for onigiri that I am addicted to is American barbequed pulled pork. As I'm stuck in landlocked Kansas, traditional ingredients have a ways to travel to reach me so I had to come up with my own combination. It is excellent as the barbeque keeps well and has fantastic flavor. I hope you all like this. Even though my heritage is Germanic, I've enjoyed studying Japanese traditions here & wanted to share my own discovery.

I just made two different sets of Onigiri, the first seemed fine but i put too much salt and the second seemed way too hard and dry :/ and the avocado crab dip I put in the middle as a filling seems to have been absorbed by the rice. Am I squeezing too hard? over cooking? btw the second batch was so sticky I had to keep rinsing my hands off

Thanks for this page I'm in the 8th and love making Japanese dishes and bentos and get up super early just to make my lunch (even though my mom scolds me for waking up so early ^_^). But I was wondering can I use Nishiki rice.

Hello,
I thought I would share a little innovation we have come up with.
I keep pre-cooked shrimp (as they come from the super market), cut pieces of pre-cooked salmon (that I buy at the deli) and frozen balls of tuna salad in the freezer in containers.
In the morning (my rice cooker cooks on timer overnight), I simply grab one filling, add a bit of mayo or spicy mayo if it's for the boyfriend, and make my onigiri with the frozen filling. By lunch time everything is perfect and thawed through.
We discovered this when we got frustrated that making a cans worth of tuna salad for a few onigiri was too much but it goes off too quickly to get through (not to mention you aren't meant to eat that much tuna in any given week). So we tried freezing it in an ice cube tray (a silicon one, smaller than regular cubes, ours is little balls), covered in saran wrap. After 24 hours or so we empty the ice cube tray into a tupperware and leave it in the freezer door and presto, instant onigiri fillings anytime you want. I recommend making it a little on the "dry" side, with less mayo than usual, and then adding a squirt of mayo when you prepare your onigiri. We add onions etc to ours before freezing and it tastes yummy.
It also makes me worry a little less about putting tuna-mayo in a warm onigiri and then leaving it in a lunch bag all day--it makes me feel the "safe" time is a little longer since it spends its first little while just defrosting.

My onigiri fell apart, what did I do wrong?
I bought sushi rice from an asian store. Washed it 3-4 times according to your method, let it dry for 30 minutes, let it soak in water for an hour (although I have no clue why it should be dried before that...), and cooked it, just like you wrote.
Unfortunately, when I put the finished rice in a bowl, the bottom wad a little burned. Not enough water? Then I mixed the sushi vinegat in it, and formed my first onigiri. Fell apart, as I said :( .
What did I do wrong? Would it need more soaking time before cooking?

Moreover, it didn't taste like anything... I used dasho powder for the cooking, and it smelled SO fishy, I thought I used way too much! And of course the sushi vinegar. But the finished onigiri had no taste, not fishy, nothing.
Any idea, please?

Well first of all, it looks like you were trying to make sushi, not onigiri. See the last bullet point above under Other Questions. Once you mix in vinegar (and cook the rice with dash) you're cooking shari, or sushi rice. __Onigiri uses plain steamed rice__. Although mixing in the vinegar flavoring shouldn't necessarily make your rice fall apart.

There are any number of reasons why your onigiri didn't turn out right. Your cooked rice could have been too dry, either from overcooking or not enough water. The rice may not have been warm enough when you tried forming the irce.

If you are interested in learning how to properly cook rice and how it should look and taste in lesson format, you may want to take the Rice Week section of the Japanese Cooking 101 course we're just starting over on JustHungry; Rice Week will be next week (the week of March 11).

The rice was pretty warm, so that should be no problem. Okay, but maybe too dry, so longer soaking time and more water for the cooking, right? And less heat during cooking. I'll try that one more time and look at the link you gave me!
Thx for the answer!